Internal combustion engine manufacturers are constantly seeking to increase power output and fuel efficiency of their products. One method of generally increasing efficiency and power is to reduce the oscillating mass of an engine, e.g., of the pistons, connecting rods, and other moving parts of the engine. Efforts to increase engine power and/or efficiency also may also result in an increase in pressure and/or temperature within the combustion chamber during operation.
Engines, and in particular the pistons of the engine, are therefore under increased stress as a result of these reductions in weight and increased pressures and temperatures associated with engine operation. Piston cooling is therefore increasingly important for withstanding the increased stress of such operational conditions over the life of the engine.
To reduce the operating temperatures of piston components, a cooling gallery may be provided about a perimeter of the piston. A coolant such as crankcase oil may be introduced to the cooling gallery, and may be distributed about the cooling gallery by the reciprocating motion of the piston, thereby reducing the operating temperature of the piston. In these approaches, conduction of heat downward away from the combustion chamber is emphasized by carrying away heat via the coolant.
At the same time, the cooling galleries may increase overall complexity of the piston assembly and manufacturing of the same. Moreover, cooling galleries require coolant to be circulated through the galleries during engine operation, in turn increasing the complexity of the engine. While cooling effects of fluid cooling galleries are significant, pumping losses associated with the need to circulate coolant through the cooling galleries are also significant.
Accordingly, there is a need for a piston that reduces fluid pumping losses, while also providing robust performance and resistance to high combustion temperatures.